When a joint is damaged either from an injury event or through surgical intervention, scar tissue may form and limit the motion of the joint. This loss of motion can greatly affect a person's quality of life by limiting their ability to accomplish their normal activities of daily living. Traditionally, orthotics are separated into two categories: those that support and protect limbs and those that attempt to return range of motion to the joint by application of force.
Different joints are capable of moving in different directions, and the full range of motion of a joint depends upon the anatomy of that joint and on the particular genetics of each individual. Joint motion can generally be classified as linear or rotational. For example, linear joint motions include flexion and extension where flexion is defined as a bending of the joint and extension is often defined as a straightening of the joint. Rotational motions include pronation and supination, which is where the hand rotates around the longitudinal axis of the forearm placing the palm up or the palm down.
Conventional orthotic devices have attempted to provide support across a joint, traditionally utilizing a rigid member or hinged joint. Orthotics aim to protect the joint by supporting the joint.
Some devices use a hinge system to apply a low load force on the joint by tightening a spring and thus stretching accumulated scar tissue over a long period of time. Some use a cuff for each limb segment and are uncomfortable and must be worn for hours at a time to be effective.